Users around the world have had trouble accessing some HTTPS websites due to an error at GlobalSign, one of the world's largest certificate authorities.

As part of a planned exercise, GlobalSign revoked one of its cross-certificates that allowed end-user certificates to chain to alternate root certificates. GlobalSign operates multiple roots, which are trusted in browsers and operating systems by default, and links them together through these cross-certificates.

The revocation of such a certificate was interpreted by some browsers and systems also as a revocation of the intermediate certificates that chained back to it. This was not really the case or the company's intention.

The blocking of intermediate certificates broke certificate chains and users started receiving certificate validation errors when trying to access websites with GlobalSign-issued certificates.

It seems that the revocation of the cross-certificate happened a while back, but the issues became apparent Thursday when GlobalSign started providing the revocation information for it over the Online Certificate Status Protocol (OCSP).

While the CA took immediate steps to fix the issue, users might still receive certificate errors for days to come because OCSP responses are cached in browsers and servers.

"The problem will correct itself in 4 days as the cached responses expire, which we know is not ideal," GlobalSign said in a report on its website. "However, in the meantime, GlobalSign will be providing an alternative issuing CA for customers to use instead, issued by a different root which was not affected by the cross that was revoked but offering the same ubiquity."

This means that affected certificate owners could obtain new certificates from a different GlobalSign-owned root that doesn't have this problem.